1. Field of the Invention
The present invention relates to a substrate holder for use in a plating apparatus for carrying out plating of a surface (front surface) to be plated of a substrate. In particular, the invention relates to a plating apparatus for forming a plated film in fine interconnect trenches and holes, or resist openings, provided in a surface of a semiconductor wafer, or for forming bumps (protruding electrodes), which are for electrical connection to, e.g., electrodes of a package, on a surface of a semiconductor wafer. The present invention also relates to a plating apparatus provided with the substrate holder.
2. Description of the Related Art
It is common practice, e.g., in TAB (tape automated bonding) or flip chip to form protruding connection electrodes (bumps) of gold, copper, solder or nickel, or of multiple layers of such metals at predetermined portions (electrodes) of a surface of a semiconductor chip, having interconnects formed therein, so that the semiconductor chip can be electrically connected via the bumps to electrodes of a package or TAB electrodes. There are various methods usable for the formation of bumps, such as electroplating, vapor deposition, printing and ball bumping. Of these, electroplating, which can form fine bumps and can be performed in a relatively stable manner, is most commonly used as the I/O number of a semiconductor chip increases and the electrode pitch becomes smaller.
Electroplating methods can be classified roughly into a jet method or cup method in which a substrate, such as a semiconductor wafer, is held in a horizontal position with a surface to be plated facing downwardly, and a plating solution is jetted upwardly onto the surface to be plated, and a dip method in which a substrate is held in a vertical position in a plating tank, and a plating solution is injected upwardly into the plating tank and the plating solution is allowed to overflow the plating tank during plating. Electroplating using a dip method has the advantages of a small footprint and good release of bubbles which adversely affect the quality of plating, and is therefore considered suited for bump plating in which plating is performed for relatively large-sized holes and which requires a considerably long plating time.
A common conventional electroplating apparatus using a dip method, which has the advantage of good release of bubbles, is provided with a substrate holder which detachably holds a substrate, such as a semiconductor wafer, with its front surface (surface to be plated) exposed while sealing an end surface and a back surface of the substrate. The substrate holder, together with a substrate, is immersed in a plating solution in carrying out plating of the surface of the substrate.
Because the substrate holder is kept immersed in the plating solution during plating, a peripheral portion and a back surface of a substrate, held by the substrate holder, must be securely sealed so that the plating solution will not intrude into the back surface side of the substrate. Therefore, the applicant has proposed a substrate holder configured to detachably hold a substrate, in which a substrate is held between a fixed holding member and a movable holding member while an inner seal member, attached to the movable holding member, is kept in pressure contact with a peripheral portion of the substrate and an outer seal member, attached to the movable holding member, is kept in pressure contact with the fixed holding member to seal the contact portions (see Japanese Patent Laid-Open Publications No. 2004-52059 and No. 2004-76022).
In such a substrate holder, it is necessary to securely seal the connection between a seal member and a member for fixing the seal member (e.g., a seal holder or a fixing ring) in order to securely prevent leakage of liquid through the connection.
The conventional substrate holder therefore has the following exemplary construction: As shown in FIG. 1, a movable holding member 100 includes a ring-shaped seal holder 102 and two fixing rings 108, 110 for respectively fixing an inner seal member 104 and an outer seal member 106 to the seal holder 102. The inner seal member 104 is interposed between an upper surface of the seal holder 102 and the upper fixing ring 108, and the upper fixing ring 108 is secured to the seal holder 102 by tightening bolts 112, thereby bringing the inner seal member 104 into uniform and tight contact with the seal holder 102 and the upper fixing ring 108. Further, the outer seal member 106 is interposed between a lower surface of the seal holder 102 and the lower fixing ring 110, and the lower fixing ring 110 is secured to the seal holder 102 by tightening bolts 114, thereby bringing the outer seal member 106 into uniform and tight contact with the seal holder 102 and the lower fixing ring 110. When the substrate holder holds a substrate W by gripping a peripheral portion of the substrate W between the movable holding member 100 and a fixed holding member 116 while thus sealing the connection between the seal holder 102 and the inner seal member 104 and the connection between the seal holder 102 and the outer seal member 106, an inner peripheral end of the inner seal member 104 makes pressure contact with and seals a peripheral portion of the substrate W, and an outer peripheral end of the outer seal member 106 makes pressure contact with and seals an upper surface of the fixed holding member 116.
The substrate holder shown in FIG. 1, however, has been found to have problems in maintenance, especially in replacement of the seal members 104, 106. In particular, the replacement necessitates the operation of removing the used seal members 104, 106 from the movable holding member 100 by removing a total of, for example, 98 bolts 112, 114, putting new seal members 104, 106 between the seal holder 102 and the upper fixing ring 108 and between the seal holder 102 and the lower fixing ring 110, respectively, and thereafter fixing the new seal members 104, 106 to the movable holding member 100 by tightening the 98 bolts 112, 114.